Video data originally developed for television screens must be reformatted before it can be displayed on most computer displays. Television screens typically require data in 2:1 interlaced format, which means a full frame of data is comprised of two spatially and temporally offset fields, typically referred to as odd and even fields. Computer displays typically require non-interlaced data (also referred to as "progressively scanned" data). Displaying video data produced for standard televisions on personal computers therefore typically requires that the video data be converted from an interlaced format to a non-interlaced format.
In Personal Computers (PCs), the two most common conversion techniques are spatial line doubling by interpolation and field recombining. Spatial line doubling by interpolation which is embodied in a technique referred to as "Bob" supported by the Microsoft Corporation, involves taking one field at a time and spatially interpolating to obtain the missing lines, usually by averaging the line above and below each missing one. Field recombining which is embodied in a technique referred to as "Weave" supported by the Microsoft Corporation involves interleaving both fields back together to get a spatially complete frame. The former approach ("Bob") is better suited for video with high motion content but produces a clearly visible loss of resolution for relatively static scenes. The latter technique ("Weave") is better suited for relatively static scenes but produces highly objectionable artifacts called feathering or ghosting when significant motion is present.
In current and past commercially available PC systems it has generally not been possible to determine whether a live video source has motion in it or not, hence "Bob" is typically used because it produces less objectionable artifacts. Moreover, the "Bob" technique allows for a relatively low cost hardware implementation using only one line delay memory. Unfortunately, artifacts produced by the "Bob" technique still exist, the most objectionable being jagged or staircase like effects on diagonal lines and edges in an image.